1. Field of the Invention
The present invention relates to a wireless communication system operating based on beamforming. More particularly, the present invention relates to a method and apparatus for transmitting and receiving a request signal for allocation of Uplink (UL) resources considering Base Station (BS) receive beams in a UL.
2. Description of the Related Art
Wireless communication systems have been developed to support a higher data rate in order to meet the continuously increasing demand for wireless data traffic. To support the increase in data rate, technologies for the wireless communication systems have evolved to mainly improve the spectral efficiency based on communication technologies such as Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and Multiple Input Multiple Output (MIMO). However, the soaring demand for wireless data traffic may not be met only with the technologies for improving the spectral efficiency.
Recently, the increasing demand for smart phones and tablet computers and the explosive increase in the number of applications operating based thereon and requiring a high amount of traffic have more accelerated the demand for data traffic. One way to meet these demands is to use more frequency resources over a wider frequency band. Therefore, in order to secure a wider frequency band and apply it to wireless mobile communication, it is necessary to consider securing an ultra wideband frequency in the wider frequency band.
Wireless communication in a millimeter Wave (mmWave) band may suffer from an increase in propagation loss such as a path loss and a return loss due to the frequency characteristics of the mmWave band. As a result, the reach of radio waves may be reduced causing a decrease in coverage. On the other hand, the wavelength is very short due to the mmWave characteristics, making it easy to apply beamforming using a plurality of small antennas. Accordingly, the path loss of radio waves may be mitigated by applying beamforming technology to mmWave wireless communication, contributing to an increase in the reach of radio waves and an increase in coverage.
Transmit beamforming is a common method of increasing directivity by concentrating arrival areas of radio waves in a specific direction using a plurality of antennas. A set of the plurality of antennas is called an antenna array and each antenna included in the array is called an array element. The antenna array may be classified into a variety of types, including a linear array and a planar array. With the use of transmit beamforming, the directivity of signals may be improved contributing to an increase in transmission distance, and almost no signal may be transmitted in directions other than a desired direction, making it possible to remarkably reduce signal interference to users other than a specific user.
Meanwhile, a receiving side may also perform receive beamforming on received signals using a receive antenna array. The receive beamforming may also increase sensitivity of the signals received in a specific direction by concentrating received radio waves in a specific direction, and may block interference signals by excluding signals received in directions other than the specific direction from the received signals.
In a cellular system of the related art, best effort-based scheduling for a UL is achieved by allocating a Bandwidth Request (BR) channel in accordance with a contention-based operation through transmission of a BR ranging code, and by requesting a bandwidth over the BR channel and allocating UL resources. Specifically, such scheduling generally considers the contention due to a multiple access by multiple Mobile Stations (MSs). An MS desiring UL transmission anonymously transmits a randomly selected BR ranging code (i.e., BR code), and upon receiving the BR code, a BS allocates, to the MS, UL resources to be used to send a message such as a Bandwidth Request Header (BRH) including a Bandwidth (BW) allocation request of the MS, and then checks information about the MS from the BRH received from the MS and the requested UL resources, and allocates UL resources for data transmission.
The cellular system of the related art basically considers equi-directional or omni-directional transmission/reception of a BS and an MS. Therefore, UL and Downlink (DL) beamforming is not considered for transmission of a BR code over a BR channel, transmission/reception of UL resource allocation information for BRH transmission, and transmission of a BRH message. Therefore, there is a need for technology for efficiently performing a series of UL scheduling procedures in a beamforming-based wireless communication system.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.